High-speed Access Control for XML Documents

One of the important tasks of managing eXtensible Markup Language (XML) documents is to uniformly specify and securely maintain both target documents and authorization policies. However, since existing techniques decouple access authorization from query processing, the query processing time with access control is not satisfactorily fast. The access control requires the overhead in addition to the time required for query processing, and the powerful expression of authorization policies makes it impossible to accelerate the determination of access authorization. In this paper, we propose a bitmap-based access authorization technique for both fast and secure services of XML documents. The authorization policies are encoded into a bitmap index and further to be coupled an index of XML documents. User access requests are encoded into bitmap-masks. By applying bit-wise operations of a bitmap-mask to the authorization bitmap index, authorization can be determined significantly fast. The contribution of this paper includes 1) the dual goals achieved for fast and secure accesses to XML document collections, and 2) early propagation of subjects and objects in bitmap indexes.